| Our country has a great prospect of marine resources development because it has nearly 3million square kilometers of sea area.The contribution of marine economy to the national economy continues to increase,and with the promotion of the strategy of a strong maritime nation,it has become the top priority in our economic development.As a kind of with good plasticity and low cost,carbon steel is very important for the construction of marine facilities.However,carbon steel is prone to corrosion in the process of use,which not only causes the waste of resources,but also limits the economic development.Coating protection technology is the most simple,economical and effective method to protect carbon steel from corrosion.Among them,self-healing coatings have become the focus of research because of its advantages of active self-repairing and long-term corrosion resistance.In this paper,polyurethane modified epoxy self-healing coatings were prepared using mesoporous titanium dioxide nanoparticles(MTNs)as green nanocontianers loaded with several safe and friendly corrosion inhibitors.The self-healing coatings were coated to the surface of carbon steel,and their corrosion protection properties and self-healing mechanism were investigated.The main research work is as follows:Epoxy coating(EP)containing MTNs(MTNs/EP)and EP containing MTNs loaded with2,5-dimercapto-1,3,4-thiadiazole(DMTD)(DMTD@MTNs/EP)were prepared on carbon steel surface.Anti-corrosion properties and self-healing abilities of these two coatings were investigated.Firstly,MTNs were synthesized by solvothermal method,and the corrosion inhibitor DMTD was loaded into MTNs.The structure of MTNs before and after loading the corrosion inhibitor was studied by transmission electron microscopy(TEM),X-ray diffraction(XRD)analysis and Fourier transform infrared spectroscopy(FTIR).The dispersion of MTNs in epoxy coating is good,and irregular bending morphology is shown in the cross section of the coating.These enhance the toughness of the Epoxy resin.The release behavior of DMTD from DMTD@MTNs in 3.5wt%Na Cl solution with different p H values was evaluated by UV-vis.The results show that the maximum release concentration of DMTD was found under basic condition(p H 10).The anti-corrosion properties of MTNs/EP with different content of MTNs were investigated by electrochemical impedance spectroscopy(EIS).The results show that the EP coating added with 0.5%MTNs(0.5%-MTNs/EP)has better shielding properties compared with the pure epoxy coating.The low-frequency impedance modulus of 0.5%-MTNs/EP is still1.0~7×10~9Ω·cm~2 after 40 days of immersion.The EIS and SEM results reveal that DMTD@MTNs/EP has good corrosion resistance and self-healing properties.Finally,the self-healing mechanism of DMTD@MTNs/EP is proposed.EP containing MTNs loaded with Phen and Tpp were prepared on carbon steel(Phen-Tpp@MTNs-PDDA/EP).The corrosion inhibition properties of Phen,Tpp Phen and Tpp were investigated by potentiodynamic polarization.The results show that the two inhibitors have"synergistic effect".They possess better corrosion inhibition effect on carbon steel compared with single corrosion inhibitor(Phen or Tpp).The release behavior of corrosion inhibitors from MTNs encapsulated with polydimethyl diallyl ammonium chloride(PDDA)was investigated.The release amount of Phen and Tpp in 3.5wt%Na Cl was p H 10>p H 4>p H 7.The self-healing properties of Phen-Tpp@MTNs-PDDA/EP were investigated by EIS combined with SEM.In addition,the sensing properties of the coating were observed by scratch experiments.The results show that the coating has good self-healing properties and self-sensing abilities.Finally,the self-healing mechanism was discussed.Anti-corrosion performance and self-healing abilities of MTNs epoxy coating loaded with Phen and gallic acid(GA)(GA-Phen@MTNs/EP)on the surface of carbon steel were systematically investigated.The release mechanism of corrosion inhibitor was explored by UV-vis.The results indicate that the responsive release of Phen and GA is based on acid and base.The corrosion inhibition properties of the Phen and GA inhibitors were investigated.The results show that both GA and Phen can be adsorbed on the surface of carbon steel to inhibit the corrosion of the carbon steel substrate.Compared with other control samples,the substrate immersed for 15 h in the GA-Phen@MTNs extract exhibits the highest low-frequency impedance modulus,the lowest corrosion current density and the highest self-corrosion potential,suggesting the best corrosion inhibition effect.EIS test results show that GA-Phen@MTNs/EP has good self-healing ability,which greatly improves the corrosion protection ability of carbon steel matrix. |
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